1. 245
Iranian Journal of Otorhinolaryngology, Vol.25(4), Serial No.73, Sep 2013
Case Report
Giant Keratocystic Odontogenic Tumor: Three Cases and
Literature Review
*
Alexandre Caixeta Guimarães1
, Mariana Dutra de Cassia Ferreira Santos1
, Guilherme
Machado de Carvalho1
, Carlos Takahiro Chone1
, Leopoldo Nizam Pfeilsticker1
Abstract
Introduction:
A keratocystic odontogenic tumor is a benign intra-bone mass originating from dental lamina or its
residue. It represents 2–11% of jaw cysts, and has a slow but aggressive growth. The evaluation of
molecular characteristics, immunohistochemistry, and genetic expression currently have no
established classification regarding the evolution and pathophysiologic pattern of these lesions.
Case Report:
This is a clinical retrospective study with a full analysis of patient history regarding physical
evaluation, radiologic images, pathology results, and surgical resection. We performed a major
literature review concerning current concepts relating to its biological characterization. Three
cases of keratocystic odontogenic tumor were identified. Two of the cases were large, with
aggressive behavior and significant bone destruction and recurrence, which had been overlooked
for more than a decade. The third case had an early diagnosis, and the treatment led to full
recovery and complete healing.
Conclusion:
The keratocystic odontogenic tumor is a benign lesion with slow growth, which lends itself to a
more conservative treatment, even in cases of large lesions. A better understanding of these
tumors, both at the biological and molecular level, could lead to guidelines for treatment and
prognosis of such patients.
Keywords:
Keratocystic tumor, Jaw, Mandible, Odontogenic tumor
Received date: 25 Dec 2012
Accepted date: 20 Jun 2013
1
Department of Otorhinolaryngology, University of Campinas (UNICAMP), School of Medical Sciences (FCM),
São Paulo, Brazil.
Corresponding Author:
Jose Ponchio Vizzari street, 303 – CEP: 13085-170, Campinas, São Paulo, Brazil.
Tel: + 55 19 82353760, E-mail: alecgxl2@hotmail.com

2. Caixeta Guimarães A, et al
246 Iranian Journal of Otorhinolaryngology, Vol.25(4) Serial No.73, Sep 2013
Introduction
Odontogenic tumors are considered rare
neoplasms, with a challenging diagnosis and
treatment. The numerous publications
concerning these tumors tend to be case
reports with unusual histopathologic or
clinical behavior. Furthermore, publications
prior to 2006 were based on the 1971 World
Health Organization (WHO) histological
classification.
In 2005, the new histological classification of
odontogenic tumors by the WHO reclassified
the odontogenic keratocyst as benign intra-
osseous neoplasia, calling it a keratocystic
odontogenic tumor (KOT) (1). Originating
from the dental blade or from its residue, this
tumor affects the bearing areas of the teeth
(2), and represents 2–11% of all mandibular
cysts. Occurring at any age, these tumors are
more common in men than women, at an
approximately 2:1 ratio, and are very
aggressive locally, with recurrence rates
ranging from 3–60% (3). Although some
KOT characteristics are considered typical of
neoplasias, particularly the high proliferation
rate of the epithelial cells, its behavior and
treatment remain controversial (4).
Recent molecular and genetic investigations
targeted towards odontogenic tumors,
especially the KOT, suggest its biological
origins, thus broadening the understanding of
its pathophysiology (1). Although the
recurrence of prognostic factors based on
clinical pathological and immunohisto-
chemical features remain undetermined; their
use may become an important assessment of
this neoplasia behavior, and may, eventually,
define a personalized treatment approach (5).
We describe three KOT cases, including two
large cases with aggressive behavior, and
review the current knowledge regarding their
biological characterization.
Materials and Methods
This is a retrospective clinical study, which
evaluated three patients at the Maxillo-Facial
Surgery Service from the Department of
Otorhinolaryngology Head and Neck at the
University of Campinas Teaching Hospital
(Campinas, Sao Paulo, Brazil) during 2011.
The work consisted of a complete review
of medical records from patients who
underwent surgical treatment for mandibular
lesions with a final diagnosis of KOT, in
addition to a literature review regarding its
biological characterization.
All patients underwent preoperative 3D
reconstruction computed tomography (CT)
scans followed by surgeries, performed by the
same team, with histopathological diagnostic
confirmation. They were followed
postoperatively with clinical and radiographic
control. Two cases presented large and
aggressive behavior lesions, with distinct
evolutions.
A medical literature review was performed
using PubMed/ MedLine, without research
limits, with the MesH terms: keratocystic
tumor; mandible; odontogenic tumor,
immunohistochemistry. This study followed
the institution Ethics Committee guidelines.
Case 1
A female patient, 53 years of age, with a 1-
year history of bulging in the left ramus of the
mandible, noticed after dental treatment,
without any pain, bleeding, limited mandibular
movement or weight loss complaints. The
patient had no other history of disease.
During a physical examination an
enlargement was noticed in the left ramus of
the mandible region, approximately 8 cm
wide, painless, without involving the mouth
floor, the gingivolabial sulcus, teeth, or
cervical lymph nodes.
A CT scan showed an insufflated lytic
formation in the mandibular left ramus and
angle, approximately 7 cm wide with the
presence of thinness and rupture of the
medial cortical with hypodense content and
related dental elements preserved. The
patient underwent surgical resection with

3. Giant Keratocystic Odontogenic Tumor
Iranian Journal of Otorhinolaryngology, Vol.25(4) Serial No.73, Sep 2013 247
complete removal of the intraoral cyst with
thickened capsule filled with cornea
formations. Histological analysis confirmed
the KOT diagnosis. The left inferior alveolar
nerve was identified and preserved. No
grafts were used and complete regeneration
of the surgical cavity was observed 4 years
after the procedure.
Case 2
A female patient, 28 years of age, with
complaints of bulging, pain, and hyperemia
in the right mandibular angle region for 18
years and pus drainage recurrence in the oral
cavity, always with spontaneous resolution.
The lesion evolved with increasingly
frequent relapses, bulging progression,
worsening pain, difficulty in opening the
mouth, and episodes of hypoesthesia in the
right inferior alveolar nerve territory. No
fever, weight loss or other complaints were
reported. During a physical examination we
observed bulging of approximately 10 cm in
the body region and angle of the right
mandible which was firm, painless, and
without signs of inflammation. The buccal
opening decreased by an average of 2.5 cm.
Neck palpation was without alterations.
A CT scan showed expansive formation of
approximately 5 cm in the ramus and the
right angle region of the mandible with well-
defined bone limits which was insufflated
with hypo-attenuation and medial cortical
rupture in the 3D reconstructions. The cuts
without reconstruction presented no
trabeculations or calcifications. There were
no remaining teeth in the lesion.
The lesion excision was performed
intraorally, and was histologically diagnosed
as a KOT; thus, confirming widespread
erosion of the mandibular cortical bone
corresponding to the lateral and medial cyst
wall. Complete removal of the tumor was
impossible to ensure in these sites and the
bipolar cauterization of soft tissues was
liberally used. The inferior alveolar nerve
was not identified, and no cavity filling
was used.
A year after the initial surgery, a control
CT scan showed persistence of the cystic
area in the right ramus of the mandible
approximately 7.5 cm in diameter, despite
the evident thickening of the cortical basilar.
Suspicion of a tumor recurrence was
confirmed by subsequent histological
analysis. Recently, the patient underwent
resection of the residual lesion with removal
of laminated white scaly tissue from the
affected area, in addition to peripheral
osteotomy reaching the bone with healthy
appearance. There was no requirement for
the use of reconstruction plates or any other
kind of cavity fillers. The patient underwent
a 6-month observational period without
signs of recurrence (Fig.1).
Fig1: Illustration of Case 2.1: CT 3D
reconstruction showing the substantial erosion
in the right jaw. 2: Alternative view from the
CT reconstruction. It is possible to note that
the mandibular nerve is very close to the
lesion. 3: Physical findings in the patient. Note
the bulging in the right side of the jaw.
Case 3
A male patient, 60 years of age, with a
20-year history of progressive bulging at the
right angle of the mandible and chewing
pain for approximately 1 year. He reported
no bleeding, weight loss, or cervical masses.

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248 Iranian Journal of Otorhinolaryngology, Vol.25(4) Serial No.73, Sep 2013
During a physical examination, we noticed
a disfiguring angular bulging in the right
mandibular, approximately 10×7 cm in size.
This was indurated, painless, and
jeopardizing the region of the mouth's floor
and swelling the sulcus and the gum border.
No neck lymphadenopathy was detected.
A CT scan showed a cystic formation in the
region of the angle and the right ramus of the
mandible, approximately 8.0 cm wide, with
irregular and inflated bone contours, in the
presence of thin bone trabeculae, with
evidence of cortical disruption, hypo-
attenuating content without dental residues,
and destroying the entire coronoid process.
The patient underwent tumor surgical
resection via the intraoral route. We
performed KOT confirmation in the frozen
biopsy and in the final microscopy
examination from paraffin. During surgery
we observed substantial bone erosion, thin
trabeculations, and numerous characteristic
corneas structures. All the remaining bone
from the ramus, angle, and coronoid process
was removed by progressive osteotomy. The
mandible was rebuilt with a 2.4 titanium
plate, without bone grafts. We chose to
sacrifice the inferior alveolar nerve involved
by the tumor along its path. After 30 days,
there was partial exposure of the plate
portion within the oral cavity without
evidence of infection or related complaints
from the patient, who recovered the
mandible contour, maintaining proper
chewing. After a 9-month follow-up, no
signs of recurrence were detected (Fig. 2).
Fig2: Illustration of Case1. 1: CT 3D
reconstruction shows substantial erosion with
irregular borders. 2: Alternative view from CT
scan showing an approximately 8-cm lesion. 3:
Coronal plan from CT showing thin bone
trabeculae, evidence of cortical disruption, and
hypo-attenuating content without dental
residues and destroying the entire coronoid
process. 4: Physical findings in the patient,
showing bulging in the right mandibular of
approximately 10×7 cm.
Discussion
As a lesion displaying more aggressive
behavior when compared to other
odontogenic cysts, the KOT presents, among
other histopathological features, a layer of
parakeratinized epithelium of lining which
distinguishes it from other cysts with
epithelial odontogenic cysts, called orthokera-
tinized odontogenic cysts. With only partially
elucidated histopathogenesis, these cysts are
considered as separate entities. In order to
better understand them, Aragaki evaluated
the immunohistochemical profile from the
keratin expression in each one (6).
In a series of 32 surgically treated KOTs,
Kuroyanagi observed significant expression
of Ki-67 and p53 in the group with
recurrences, suggesting that the evaluation
of these marker proteins helps inform the
decision regarding adjuvant procedures and
that it has a prognostic value (7). According
to Mendes, in the rapidly induced markers
study, response to growth factors, tumor
promoters, cytokines, bacterial endotoxins,
oncogenes, hormones, and stress, such as
COX-2, can increase our knowledge on the
biological mechanisms involved in the
development of these tumors (1).
Anticipating the proposition of future
therapies, Zhang postulated that the
development of synthetic active receptor
antagonists or transcription factors from the
Sonic hedgehog (SHH) signaling pathway
may result in an effective treatment for this
tumor.
He suggested that inhibition of the
Smoothened (SMO) by intracystic injection

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Iranian Journal of Otorhinolaryngology, Vol.25(4) Serial No.73, Sep 2013 249
of a protein antagonist would be the
treatment with the greatest potential (2).
For small KOTs, the most conservative
procedure available (usually enucleation)
would be mandatory. Endoscopic removal
allows the careful exploration of difficult-to-
reach areas through direct visualization,
allowing not only the monitoring of the wall
separation between the tumor and the inferior
alveolar nerve, but also promoting the
complete removal of the lesion (8). For larger
tumors with bone cortical, coronoid process,
or mandibular incision destruction, some
authors suggest radical resection including
transfacial access (9). In the cases described,
we observed that the larger tumors were the
result of years of negligence. The benign
nature of these tumors is associated with the
slow evolution and prospect of a possible
recurrence, which leads to a more
conservative attitude even in the presence of
larger lesions. The presence of bone cortical
erosion would be a negative prognostic
factor. Although present in all our patients,
we question whether it would be the product
of more aggressive tumor or simply an
expression of the longer evolution period.
In resections resulting in large residual
fragility of the mandible, we recommend, as
a preventive measure for possible secondary
fracture of the bone, reinforcement with 2.4
titanium plates overlapping the lesion area,
similar to the one from the reported case.
With the expectation of substantial bone
removal and interruption of the continuity,
we suggest placing a plate before the tumor
resection is finalized, since there is no
requirement for en bloc removal. Therefore,
a better quality mandibular reconstruction is
accomplished by maintaining the correct
positioning of the distal fragments
associated with the condyle, particularly in
the complete edentulous. The mandibular
evaluation with computerized densitometry
after the KOTs enucleation, showed
progressive regeneration of the defect area
without any grafting material, with a more
significant increase in bone density 6
months after the surgery (10). Consistent
with others authors (11), we believe that
spontaneous bone regeneration occurs even
in larger mandibular defects; and thus, in
our patients, we do not use grafts or any
kind of bone formation stimulating
products.
Owing to the frequent recurrence, a variety
of adjuvant treatments have been proposed,
including the removal of the peripheral bone
(osteotomy), en bloc resection of the cyst
with the surrounding bone, cryotherapy
(freezing) with liquid azote, and use of
Carnoy's fixative solution into the cavity
after the enucleation. For Madras, a
resection or enucleation supplemented with
Carnoy's solution, with or without
osteotomy, would result in a lower
recurrence than with the enucleation or the
marsupialization alone. However, the
recurrence after marsupialization followed
by enucleation did not differ from more
aggressive therapies (12). In another study,
Morgan noted that osteotomy with or
without the use of Carnoy's solution showed
a lower rate of recurrence compared with
enucleation with or without the use of the
same solution (13). In a retrospective
analysis of a total of 68 patients, Zecha
observed recurrence in 40% of the 10
marsupialized tumors with a follow-up of 58
months, and in 20.7% of the 58 enucleated
with follow-up averaging 46 months (14).
Because of the high recurrence rates, the
author believes that further studies should
investigate the possible benefits of
supplementary treatments, especially the
Carnoy's solution. Despite these reports, in a
large systematic review of all literature
related to the treatment of isolated KOT of
the maxilla and the mandible, Sharif found
no relevant published randomized controlled
trials and states that no conclusion can be
inferred regarding the effectiveness of these
adjuvant interventions (3). The definition of
the KOTs epithelial histological pattern and

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250 Iranian Journal of Otorhinolaryngology, Vol.25(4) Serial No.73, Sep 2013
the expression of keratin raise questions
about previous studies which sought to
clarify the associated factors with these
tumors recurrence; however, these works
were probably associated with different
types of lesions in their casuistry. In a
retrospective study of 120 patients submitted
to a simple enucleation and evaluated over a
10-year period, Pitak-Arnnop observed
tumoral recurrence in 28 patients (26%),
among which seven (6%) were multiple
recurrences. However, the study did not
identify a significant association with the
radiological findings, the histological type,
cortical perforation, or the lesion location
(P>0.05) (15). In this study, the authors state
that only 80 lesions showed parakeratosis, a
fact that allows us to question whether the
remaining cysts were in fact orthokeratinized,
a lesion with a different evolution from the
KOTs. In another study with patients treated
for tumor decompression, August (16)
observed the disappearance of the epithelium
and interruption of the cytokeratin-10
production in 64% of cases; thus,
questioning whether this change would be
associated with lower recurrence rates.
However, a recent study considers that the
cytokeratin-10 expression would not occur
in KOTs, but in orthokeratinized odontogenic
cysts instead (6).
Boyne proposed an interesting thesis
involving seven patients with multiple
recurrences over a period up to 21 years. In
this work, he highlights the histological
analysis performed in resected
hemimandibles from patients operated on
several times, in which, besides the
recurrence on the edges of old lesions, the
presence of other lesions was also verified in
different locations. From these observations,
the author establishes the multifocal nature of
the KOTs, and emphasizes that recurrences
were not necessarily related to the surgeon's
skills, but to the very nature of the lesion (17).
We believe that further studies are needed to
confirm these findings, but this behavior
would undoubtedly be consistent with the
current knowledge involving the biological
behavior of KOTs.
Although extremely rare, it is important to
remember that there are reports of squamous
cell carcinomas derived from odontogenic
keratocystic tumors (18).
Conclusions
The benign nature of these tumors and
their slow evolution justify conservative
treatment, even in the case of large lesions.
The knowledge relating to the biological
profile of the KOTs is of great importance
in order to better understand the evolution
of these lesions; thus establishing more
precise treatment and prognosis.
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